<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>逛水果店</title>
</head>
<style>
  * {
    margin: 0;
    padding: 0;
  }

  div {
    text-align: center;
  }

  table {
    margin: 0 auto
  }
</style>

<body>
  <div id="app">
    <h4>欢迎光临_vue开发的收银系统_水果店</h4>
    <table border="1" width="600" height="100">
      <caption>
        苹果10￥/斤，折扣/《8折》
      </caption>
      <tbody>
        <tr>
          <td>
            <span>请输入你要购买的斤数</span>
            <input type="number" placeholder="请输入斤数" v-model.number="count" />
          </td>
        </tr>
        <tr>
          <td>
            <button @click="add">结账买单</button>
          </td>
        </tr>
      </tbody>
    </table>
    <p>结账单：总价:{{pirse}}元 折后价:{{pirse*0.8}}元 省了:{{pirse-pirse*0.8}}元</p>
  </div>
</body>

</html>

<script src="https://cdn.bootcdn.net/ajax/libs/vue/2.7.14/vue.js"></script>
<script>
  new Vue({
    el: '#app',
    data: {
      count: '',
      pirse: ''
    },
    methods: {
      add() {

        this.pirse = this.count * 10

      }
    }
  })
</script>